Abstract: Promoting the integrated development of carbonreduction, pollution reduction, green expansion, and economic growth is essential for achieving sustainable high-quality development in the Yangtze River Economic Belt (YREB). A multidimensional evaluation framework integrating these dimensions was developed using panel data from 11 provincial regions (2011-2022). Through integrated application of extended measurement model, geographic detector model, and spatiotemporal geographically weighted regression (GTWR), the synergistic effects and spatial-temporal heterogeneity of the influencing factors were systematically investigated. The results indicated: (1) The synergistic development levelof pollution reduction, carbon mitigation, vegetation expansion, and economic growth in the YREB exhibited a fluctuating upward trajectory, with the regional collaborative development mechanisms progressively exerting their effects.(2) Four pivotalfactors, including R&D intensity, industrial structure, energy intensity, and foreign investment, collectively established the critical framework for coordinating environmental and economic development in this region. (3) Energy intensity and R&D intensity exerted stronger influences than industrial structure and foreign investment, while downstream regions exhibited more pronounced negative effects from R&D intensity and foreign investment. (4) Region-wide analysis revealed sustained enhancement of R&D intensity effects, an inverted "U" pattern in industrial structure coefficients, unstable energy intensity effects, and underperforming foreign investment contributions.Moving forward, it is recommended that regions leverage their respective resource endowments and development stages, capitalize on their strengths, and enhance cross-regional cooperation mechanisms to comprehensively promote a balanced development between environmental protection and economic growth.